Various impact attenuation devices and energy absorbing systems have been used to prevent or reduce damage resulting from a collision between a moving motor vehicle and a roadway hazard. Potentially hazardous conditions include slow moving or stopped highway service vehicles and highway maintenance vehicles which are either on the roadway or adjacent to the roadway. Examples of prior impact attenuation devices and energy absorbing systems include various crash barriers with structures and containers having crushable elements. Other crash barriers rely on inertial forces generated when material such as sand is accelerated during an impact. A further approach includes positioning an energy absorbing system such as a truck mounted attenuator on the rear portion of a heavy duty truck or service vehicle and positioning the vehicle in front of a highway work zone.
Examples of impact attenuation devices and energy absorbing systems appropriate for use on a slow moving or stopped highway service vehicle are shown in U.S. Pat. No. 5,248,129 entitled Energy Absorbing Roadside Crash Barrier; U.S. Pat. No. 5,199,755 entitled Vehicle Impact Attenuating Device; U.S. Pat. No. 4,711,481 entitled Vehicle Impact Attenuating Device; U.S. Pat. No. 4,008,915 entitled Impact Barrier for Vehicles. Each of the preceding patents is incorporated by reference for all purposes in this application.
Various impact attenuation devices and energy absorbing systems have also been used to prevent or reduce damage resulting from a collision between a moving motor vehicle and a stationary roadside hazard. Some of these devices and systems have been developed for use at narrow roadside hazard sites such as at the end of a median barrier, edge of a roadway barrier, large sign post along the side of a roadway, and bridge pillars or center piers. Such impact attenuation devices and energy absorbing systems are installed in an effort to minimize the extent of personal injury as well as damage to a vehicle and structure associated with the roadside hazard resulting from vehicle impact with the roadside hazard. Examples of general purpose impact attenuation devices are shown in U.S. Pat. No. 5,011,326 entitled Narrow Stationary Impact Attenuation System; U.S. Pat. No. 4,352,484 entitled Shear Action and Compression Energy Absorber; U.S. Pat. No. 4,645,375 entitled Stationary Impact Attenuation System; and U.S. Pat. No. 3,944,187 entitled Roadway Impact Attenuator. Examples of specialized stationary energy absorbing systems are shown in U.S. Pat. No. 4,928,928 entitled Guardrail Extruder Terminal and U.S. Pat. No. 5,078,366 entitled Guardrail Extruder Terminal. Each of the preceding patents is incorporated by reference for all purposes in the present application.
Previous truck mounted attenuator systems suffered from problems such as vibration weakening or breaking internal adhesive joints and sagging of the system due to bond failure. Also, some prior truck mounted attenuator systems failed to perform properly as a result of absorbing moisture.